Use of dialkyl oxalates in vinylidene resins



USE OF DIALKYL OXALATES' IN RESINS Robert J. Reid, Canal Fulton, William Mayo Smith, Jr., Cuyahega Falls, and'Byron H. Werner, Akron, Ohio, assignorsto The Firestone Tire '& Rubber Company, Akron, Ohio, a corporation of Ohio No Drawing. pplication February 23, 1954 Serial No. 412,071

9Claims. (c1. 260 -31.8)" i.

' which will. lower the processing temperature below the critical range without having any undesirable efiect on the products obtained.

Such resins are characterized by crystalline, behavior,

i. e., they fuse sharply toform relatively fluid melts; On

- quenching and. orienting,.the extruded filaments and films are crystalline in character. A syndrome of this crystalline habit is the recalcitrance of these resinsto compounding: The macro-molecules of these resins prefer contact with each other and tend to reject any foreign substances such as plasticizers and the like. In the random structure obtained without orientation any added ingredient of limited compatibility, such as the processing aids of this invention, is retained in larger percentagesthan is possible in the stretched or oriented products. On stretching, the tendency toward exudation or spewing is considerably increased. In orienting films and filaments or vinylidene resins they are stretched to several times their original length, and ordinarily until there is a sharp rise in the modulus. It is difiicult to provide suitable processing aids which do not exhibit an undesirable spew or bloom on the surface of the oriented products and which in addition Un S ate Pam 1Q) Patented Nov. Q, 1958 'fluoride,'vinyl acetate, styrene, acrylic and methacrylic esters such as methyl methacrylate, ethyl methacrylate and the like, acrylonitrile, vinyl-type ethers and ketones such as methylvinyl ether, methylvinyl ketone and related compounds such as methylisopropenyl ketone and the like. For a more complete list of compoundsknown to copolymerize with vinylidene chloride 'to produce resins which can be plasticized as herein described, see Krczil, Kurzes Handbuch der Polymerisationstechnik, vol; II, "Kehrstoftpolymerization, Edwards Bros Inc., p. 739, the items indented under vinylidenechloridi The processing aids of this invention are the dialkyl oxalates, the alkyl groups of which each contain three to seven carbon atoms. They have excellent light stability and good heat stability as well as good spew resistance. They are non-toxic,non-allergenic, and relatively odorless. In addition, they do not appreciably increase the tendency of oriented films or filaments .to shrink when exposed to elevated temperatures,

' amount, in the range of 3 to 8 percent or upto v1 0 perpossess good heat and light stability or which .at least are not detrimental to such stability.

Thus, the problem of providing processing aids for these crystallineresins is complicated not only by thefact that they tend to reject and spew the majority of conventional plasticizers, but, because the resins are extrudedas hot melts at temperatures in the neighborhood of, for example, 170" C., many conventional resin-compounding ingredients tend to decompose or react with other compounding ingredients which are present when the resins are maintained in a molten state immediately prior to and during extrusion.

The crystalline resins to which the processing, aids of this invention are added include both horn-opolymers of vinylidene chloride and copolymers thereof with not morethan substantially 15 percent of other ethylenically unsaturated compounds copolymerizable therewith. The copolymers contain at leats substantially 85. percent of vinylidene chloride. Suitable comonomers for the copolymerization include, for example, vinyl chloride, vinyl cent based on the weight of the resin will generally be found most satisfactory. Less than 3 percent may be used in'admixture with another processing aidJl Such percentages will be stably retained'within the resin in the finished oriented article. The lower membered esters show a lesser tendency to spew (greater compatibility with the resin) than the higher membered oxalate esters.

' Thus a dipropyl oxalate can be used in greater amounts than a diheptyl oxalate without showing a spew'tendency. In nocase' will more than about 10 percent of the processing aid be employed in a vinylidene resin because such larger amounts are incompatible and exude to the surface of oriented products produced from vinylidene polymeric resins containing 85 percent or more of vinylidene chloride. r

The dialkyl'oxalates can be employed with the epoxy heat stabilizers such as glycidyl-phenylether, the mono-, di-, tri-, tetra-, and penta-chlorinated derivatives of phenoxypropene oxide, polymeric phenoxy compounds prepared from various dihydroxy phenols vand epichlorhydrin, etc. Likewise, they can be employed with the light stabilizers which are esters of salicylic acid such as phenyl salicylate,

4-tert-butylphenyl salicylate, 4 octyl phenyl salicylate,

Z-methyl phenyl salicylate, 4-chloro phenyl salicylate, 3-methyl phenyl salicylate,-4-tamyl phenyl salicylate, 4-nonyl phenyl salicylate, 2-'octyl-4- methyl salicylate, 2-isopropyl salicylate, nonyl salicylate, ethylhexyl salicylate, n-butyl salicylate, etc.

The dipropyl, dibutyl, diamyl, dihexyl anddiheptyl oxalates all impart desirable extrusion properties'to the I Crystalline resinous copolymer of vinylidene ehl'o.

resins and are retained in the extruded, oriented products. They have no adverse efiect on light or heat stability, and may actually assist in their action Test data'was compiled from compositionsbothiwith and without light and heatstabilizers according to the following formulation:

1 Parts by weight ride and Vinyl chloride (:l 5)

V be noted as an oily streak on theglassine.

The additives were ball milled with the resin, and sam:

ples tested for heat stability, light stability, and spew according to the methods given below:

H eat' stability Five grams of the composition to be tested were charged into a compression mold of Hastelloy C (a 55/20/6/14/5 Ni/Mo/Fe/Cr/W alloy) in-the form of a. cylinder 1.25 inches in diameter. .flThe-molding cycle was- (1) Heat for three minutes with steam at 120 lbs/sq.-

in. and mold pressure of 1000 lbs./sq./in.;

, v to spew, and above the levels mentioned cannot be accept- (2) Water cool for two minutes under 1000 lbs/sq.

in. mold pressure; and

(3) Ejectfrom the press.

The resultant cylindrical button (1.25 inches in diameter and .l- .188 inch in height) was then cut into I sector-.shaped-specimens which were placed in a forced-.

draft oven at 180 C. Specimens were removed at intervals of 10, 20, and minutes after placing'in the oven, and the behavior of the specimens on the test asa whole was rated by the operator.-

Light stability One gram samples of the compositions to be tested were placed between Cellophane (regenerated cellulose) sheets and pressed in a flat'platen laboratory press under a total of 1000 lbs. at a temperature of 180 C., yielding a plaque approximately 6' to 8 mils thick. The plaques "were tested according to the method of ASTM 'te'st D620 T under a sunlamp for 240 hours.

Plaques were also tested in a weatherometerfor 100 hours, and 200 hours. The weatherometer was a standard X-l-A- machine, using a Corex D filter and operating without the sprays.

Spew rating A plaque of the compounded resin was pressed between Cellophane (regenerated cellulose) sheets in a Carver press at 180 C., using approximately 1.5 grams of resin,

10. seconds preheat, and 15 seconds with the minimum pressure (pressure indicator just 05 zero). was quenched in cold water immediately and an approximately inch wide strip was cut from the plaque, the

Cellophane removed, and the striporiented to its limit. The oriented strips were placed in glassine bags under mild pressure so that contact of the strips with the bag was assured. Any exudation of plasticizer could then Tests were carriedout at room temperature and at C., the latter condition tending to accentuate any migration of plasticizer. 1 v 1 V Using the oxalates of this invention, no spew was observed in this test after 56 days at room temperature.

With dioctyl phthalate instead of .the processing aid of;

this invention, definite spew occurred after one day.

' Test results It was found that the use. of the propylpbutyl, amyl, hexyl, and heptyl oxalates do not adversely, afleet the .heat and light stability of the resin compositions. In fact,

it was often observed that the deletion of the glycidyl phenyl ether (used asa heat stabilizer) and/or the 4-tbutylphenyl salicylate (used as a light stabilizer) was partially compensated 'for by the various processing aids. Oxalates in the range of dipropyl to diheptyl oxalates were chosen as processing aids because these materials do not show adverse spew under the aforementioned conditions. The light and heat stability of these esters is entirely satisfactory. Esters lower than diprQpyl have a higher volatility'and produce an odor which is slight to non-existent for the higher esters. However, esters- 1 higher than diheptyl show a markedly increased tendency after orientation.

The plaque "with a dialkyl oxalate,- as a processing aid, the oxalate being in the range of dipropyl to diheptyl 'oxalates,

' whereby'a non-exuding extruded, oriented product is obtained, the amount of the oxalate being substantial but not in'excess of about lO percent, said percentages referring to percentages by weight of the polymeric resin.

l in which the dialkyl oxalate.

j thereof with up to 15 percent of other ethylenically 2,859,194". r f i ably used.

The resins referred to herein are homopolymers of vinylidene chloride and'copolymers thereof with up to. 15 percent of other monomer copolymerized therewith.

Increasing the vinyl chloride content of the resin gives polymeric products in which plasticizers generally are more compatible. The comment herein relative to spew is to be considered in the light of the fact that homopolymers of vinylidene chloride are somewhat less compatible with the processingaids than copolymers con: taining as much as 15 percent of vinyl chloride or other monomer.

Extrusion Tests were conducted using various processing aids with g 4 to8 parts by weight of processing aid, together with '2] parts glycidyl phenyl ether-and 2 parts phenyl salicylate 5 'as light and heat stabilizers: The extrusions were carried out in conventional screw-type machines, the molten polymer being forced through dies to formflfilaments; which were then quenched by passage through a water per cent by passage "over" bath and cold-drawn some 400 diifere'ntial'speed rolls..

parts plasticizer to give desirable extrusion character istics and such filaments on storage in all cases exuded the plasticizer.

)7 The processing aids of this invention lower the melt temperature of the resin, allowing extrusions to take place The extruded products are 7 without decomposition. smooth and of uniform diameter and are free of spew What we claim is: 7 I

1. In the process of extruding and orienting a crystalline polymeric resin selected from the group consisting of homopolymers of vinylidene chloride and copolymers" thereof with up to 15 percent of other ethylenieally unsaturated monomer, the improvement which comprises extruding'and orientingthe molten resin while admixed 2. 'The process of claim is di-n-butyl oxalate. 7 1

3. The process of claim 1 in which an epoxy heat stabilizer and alight stabilizer .are used in 'the molten' resin, the light stabilizer being an ester of salicylic acid. 4. A resin composition which' includes acrystalline polymeric resin selected from the group consistingi of homopolymers of'vinylidene chloride and copolymers unsaturated monomer, and as a processing aid:a dialkyl oxalate in the range'of dipropyl to diheptyl oxalates, the

' amount of the oxalate beingsubstantial but not in excess.

, of about 10 percent, said percentagesreferringto percentage s by-weight of the polymerie resin.

5; ,The'resin composition of claim 4 inwhich the processing aid is di-n-butyl oxalate.

- 36. The resin composition of claim 4 which contains.

an epoxy heat stabilizer and a light stabilizer which is an ester of salicylic acid. V j I j A *esin composition 'which includes a copolymer of substantially"'percent 'vinylidene chloride and-15 They have. i

percent vinyl chloride, and a substantial amount not in excess of 10 percent by weight, based on the weight of the copolymer, of a dialkyl oxalate in the range of dipropyl to diheptyl oxalates, the oxalate being a processing aid for the extrusion of the resin.

8. The resin composition of claim 7 in which the processing aid is di-n-butyl oxalate.

9. The resin composition of claim 7 which contains an epoxy heat stabilizer and a light stabilizer which is an ester of salicylic acid.

6 l References Cited in the file of this patent UNITED STATES PATENTS Kvalnes V Aug. 24, 1937 Irons Aug. 2, 1949 Berry 'Oct. 11, 1949 OTHER REFERENCES Buttrey: Plasticizers, published by Interscience Inc., 10 New York, 1950, pages 59, 61 to 63. 

4. A RESIN COMPOSITION WHICH INCLUDES A CRYSTALLINE POLYMERIC RESIN SELECTED FROM THE GROUP CONSISTING OF HOMOPOLYMERS OF VINYLIDENE CHLORIDE AND COPOLYMERS THEREOF WITH UP TO 15 PERCENT OF OTHER ETHYLENICALLY UNSATURATED MONOMER, AND AS A PROCESSING AID A DIALKYL OXALATE IN THE RANGE OF DIPROPYL TO DIHEPTYL OXALATES, THE AMOUNT OF THE OXALATE BEING SUBSTANTIAL BUT NOT IN EXCESS OF ABOUT 10 PERCENT, SAID PERCENTAGES REFERRING TO PERCENTAGES BY WEIGHT OF THE POLYMERIC RESIN. 